Some electronic devices use built-in infrared (IR) circuitry in order to allow them to communicate with other devices either on a unidirectional or bi-directional basis. For example, some calculators have built-in infrared circuits which allow them to communicate with printers. While some computer keyboards use built-in infrared links to communicate with their respective computer system.
Infrared links are cost effective solutions and are especially suited for portable electronic devices given that they are fairly simply to implement, do not take up much room on the electronic device's main printed circuit board (PCB) and are fairly inexpensive to design-in.
Infrared communication links however present several drawbacks over other types of communication links, such as RS-232 serial links, etc. One drawback to IR communications is that if the two devices which are communicating with each other are placed in very close physical proximity to each other, IR distortion due to increased bit error rate may affect the communications if the IR transmitter(s) are operating at high IR power (intensity) levels. This problem typically comes about because the IR transceivers in the electronic devices may be set at a certain power level in order to guarantee IR communications at up to a certain distance (e.g., one meter) from the other device. In order to meet the distance specification, the IR transceivers are set with IR transmit power levels which will guarantee communications at the given distance (e.g., one meter, etc.), while still providing a high level of noise immunity in a typical use (e.g., office) environment. One standard setting body which sets such specifications for the industry is "The Infrared Data Association" (IrDA), which has been set up to establish standards for infrared communications. In order to be compliant with some of the IrDA standard(s), a IR transmitter must typically operate at a high enough power level to guarantee communications up to a certain distance (e.g., one meter) away from another device.
Another problem typically encountered using IR communications is found when the IR transmitters (or transceivers) are designed into portable radio frequency (RF) communication devices such as two-way pagers, personal digital assistance (PDAs) having radio communications capabilities, etc. The problem in this environment is that the embedded IR circuitry can sometimes generate noise which may affect the radio frequency transmissions of the device in question. The noise generation of the IR circuitry is sometimes worse at higher IR transmissions levels since the electronic device's power supply is more heavily loaded at the higher IR transmit power levels.
A final problem typically found with the use of IR circuitry in portable electronic devices is that in situations were the IR transmissions are set at high power levels, the IR transceiver operation will increase the battery charge times for the portable electronic devices when the electronic device is being charged, if IR communications are taking place during the charging of the electronic device. Higher IR levels for portable electronic devices also mean reduced battery life for the portable devices.